As the technology developing, the semiconductor light-emitting device has significantly contributed to information, communications, and energy conversion applications. For example, the semiconductor light-emitting device can be applied to fiber-optic communications, optical storage and military systems. For energy conversion applications, the semiconductor light-emitting device generally has three types: a device for converting electrical energy into light, such as light-emitting diode; a device for converting light signal into electrical signal, such as optical detector; and a device for converting light radiation energy into electrical energy, such as solar cell.
Growth substrate is very important for the semiconductor light-emitting device. Semiconductor epitaxial structure, which is necessary for forming the semiconductor light-emitting device, is formed on the growth substrate and is also supported by the growth substrate. Therefore, it is important to choose a suitable growth substrate for growing a high quality semiconductor epitaxial structure of the semiconductor light-emitting device.
However, a substrate suitable for growth is sometimes not suitable for support. In conventional process of fabricating the red light diode, GaAs substrate, which is opaque to red light, is used as the growth substrate, because the difference of the lattice constant between GaAs substrate and the semiconductor epitaxial structure of the red light device is the smallest. But, the opaque growth substrate reduces the light-emitting efficiency of the light device, as the light device is operated for emitting a light.
Since the growth substrate and the support substrate for the light device should meet different conditions, the technology of transferring substrate is developed. Namely, the semiconductor epitaxial structure grows on the growth substrate firstly, and then the semiconductor epitaxial structure is transferred to the support substrate for the following fabricating process. The steps of transferring the semiconductor epitaxial structure from the growth substrate to the support substrate include removing the growth substrate and bonding the semiconductor epitaxial structure and the support substrate, wherein removing the growth substrate is one of the key steps.
The method of removing the growth substrate from the semiconductor epitaxial structure includes dissolving the growth substrate by etchant, grinding the growth substrate, or forming a sacrificial layer between the growth substrate and the semiconductor epitaxial structure in advance and removing the sacrificial layer by etching process to separate the growth substrate and the semiconductor epitaxial structure. However, the growth substrate is going to be discarded no matter in the process of dissolving the growth substrate by etchant or the process of grinding the growth substrate. The growth substrate that cannot be reused means a waste in the environmentally-oriented era. So, for fabricating the semiconductor light-emitting device, if the growth substrate and the semiconductor epitaxial structure are separated by using the sacrificial layer, how to effectively implement the process of selectively transferring the semiconductor epitaxial structure is one of the research topics.